Piston pump for the conveyance of liquids



Dec. 15, 1936. R T 2,064,750

PISTON PUMP FOR THE CONVEYANCE OF LIQUIDS Filed A ril 8, 1953 2Sheets-Sheet 1 eozo 6 olna I r- I Dec. 15, 1936.

M. HURST PISTON PUMP FOR THE CONVEYANCE 0F LI QUIDS Filed April a, 19332 Sheets-Sheet 2 Patented Dec. 15, 1936 UNITED STATES rrs'ron rmur non'rim comnucn Max use. Stutt a Robert Bosch Germany F LIQUIDS Germany,assirnor to Aktiengeeeilschaft, Stuttgart,

Application April 8 1933, No. 865,228 I InGermany April 23,1932

16 Claims. (euros-s1) The present invention relates to piston pumps forthe conveyance of liquids and more especially for conveying fuel to thecarbureter or the injection pump of an internal combustion engine,

in which the pump piston is driven by a driving means arranged outsidethe fuel-conveying spaces, and is controlled by at least one movabletransmission member which acts indirectly or directly on the piston. Theinvention hasfor its object to construct the conveying pump in such away that no air can enter through the place where the transmissionmember passes into the fuel-conveying chambers, so that a satisfactoryand reliable operation of the internal combustion engine is ensured.

For this purpose, according to the invention, both sides of the pistonare exposed to the liquid (fuel), and the arrangement of the pump issuch that those chambers of the pump whose wall is traversed by amovable member of the drive acting from outside are permanentlymaintained by the liquid conveyed under a pressure correspondingsubstantially to the excess pressure in the conveying pipe.

Two examples of construction of the invention areshown in the drawings,in which:--

Figure 1 shows an injection pumping plant for Diesel engines having aconveying pump constructed in accordance with the invention.

Figure 2 shows the first example of construction of the conveying pumpin longitudinal section on the line A-B of Fig. 1.

Figures 8, 4 and 5 show the same pump in different working positions,and in section on the line C-DE-F Of Fig 2. H

Figure 6 is a diagrammatic longitudinal section of the second example ofconstruction of the conveying pump.

I is an injection pump of known construction having four separate pumps,the pump pistons 2 (Fig. 2) of which are lifted as usual by the camshaft3 mounted in the casingof the injection pump through plunger or tappetrollers l and plungers 5. The injection pump draws fuel from a filter 6arranged in advance of it, the

inlet side of which is connected through a pipe I with the pressure"side of a conveying pump 8. This latter draws fuel from the mainstorage receptacle 9 arranged below it. The conveying pump is flanged toone long side of the injection pump, and in such a way that it liestransverselyto its cam-shaft 3 (Fig. 2). The pump body III of theconveying pump projects with a tubular extension ll into the interior ofthe injection pump. A plunger I2 is guided in the extension II, and actson the piston II of the conveying pump through a strong spring I! and apush-rod ll which passes through'into the pump body I0 from the outside.The piston is guided in a passage 23 inthe pump body 10 through thebottom 5 of which the push-rod It extends co-axially with the passage.The open end of this passage is closed in a liquid-tight manner by ascrew-cap 24. At least one back pressure spring 16 acts on the piston i5and has a tendency to press it 10 against the front end of the push-rod.The plunger l2 and the push-rod ll are pressed constantly against thedriving cam II by a common spring ll bearing between the pump body andthe outer head of the push-rod, and the cam 15 serves at the same timealso for driving a pump piston 2 of the injection pump I. In the pumpcasing I! a suction valve l9 and a pressure valve 20 are arranged on theside of the piston remote from the push-rod (see Figs. 3-5). The 20movable members of these valves are formed as plates, which withoutvalve springs simply bear, on their sea owing to their own weight. A.passage 22 connects the outlet side of the pressure valve with the otherside of the piston. 25

The conveying pump described works as follows:

On the rotation of the cam-shaft 3 of the injection pump the conveyingpump 8 is simultaneously operated by the driving cam l8. Its 30 plungeri2 is moved by the driving cam against the action of the spring l1 andthe piston spring it into the interior of the pump body ID, as is shownin Fig. 3 by feathered arrows. -The movement of'the plunger is at thesame time trans- Y mitted by the push-rod M to the piston ii. In

this operation, fuel in the pump 'chamber'between the suction valve l9and the pressure valve 20 is conveyed through the pressure valve 20 whenthe suction valve is closed. A part of 40 this fuel. fills at the sametime through the passage 22 that chamber which is freed on the lowerside of the piston. This chamber is smaller by the stroke volume of thepush-rod than the quantity of fuel pumped through the pressure 45 valve.The quantity of fuel corresponding to this stroke volume is thus forcedthrough the pump outlet into the pipe I leading to the filter 6. 0n thereturn stroke effected by the two springs l6 and H, the upper side ofthe piston draws fresh fuel from the main storage container 9 throughthe suction valve l9, whilst the lower side of the piston forces thequantity of fuel received-in its pump chamber on the preceding stroke by"the 6 passage 22 through the outlet into the pipe 1, as is shownby theunfeathered arrows in Fig. 4.

If the quantity of fuel delivered by the conveying pump to its outlet ina certain period of time is greater than the fuel consumption of theinternal combustion engine (for example, when running idle), thepressure then increases behind the pressure valve 20, and thus also onthe lower side of the piston, until the back pressureexerted on the rearface of the piston l5 exceeds the pressure of the piston spring I6. Assoon as this condition is reached, the spring l6 cannot fully return thepiston l5 any longer, as is shown for example in Fig. 5. The quantityconveyed by the conveying pump thus adapts itself automatically to thefuel consumption of the engine.

, The spring I3 provided between the head of the push-rod l4 and thebottom of the plunger l2 serves as a buffer, and is of such strengththat it cannot be compressed during normal working. This spring thusprevents the transmission of shocks and the like to the push-rod ll andso to the piston l5.

In the second form of conveying pump, shown in Fig. 6, the piston i5works through two spring-loaded pressure valves 20 and II, the first ofwhich is arranged in the piston coaxially with the suction valve l9,which is also spring-loaded, and with the push-rod ll. The push-rod ishere made integral with the piston.

The mode of action of this pump is essentially the same as that of theconveying pump first described. On the downward movement of the piston,which is eifected by the back pressure spring l6, fuel is drawn throughthe valve I! from the upper side of the piston l5, whilst the fuel onthe lower side of the piston is forced away through the second pressurevalve 2| arranged in the pump body II. The pressure valve 2| provided inthe piston is at the same time closed. As soon as the driving cam llacts on the head of the push-rod M, the piston is moved against thepressure of the spring I into the interior of the pump. During thisaction the suction valve it remains closed; whilst the fuel in front orthe piston is pressed through the first pressure valve arranged in thepiston and into the chamber below the piston.

It is common to both constructions of the conveying pump that on-theside of the piston I! towards the push-rod I 4 an excess pressurerelative to the external surroundings of the pump prevails both on theoutward stroke and also on the inward stroke. In this way air isprevented from penetrating along the push-rod into the conveying pump.

The second pressure valve 2| provided in Fig. i may also be omittedwithout anything being essentially altered in the action of the pump.

I declare that what I claim is: I

l. A piston pump for conveying liquids comprisinga pump casing having aninlet passage and an outlet passage, a piston reciprocable in saidcasing, driving means adapted to loosely engage and positively displacesaid piston in one direction only, resilient means for displacing thepiston in the other direction, a suction valve controlling said inletpassage and communicating with that side of the piston remote from thedriving means and a discharge valve communicating at all times with theoutlet passage and with the side of the piston adiacent to the drivingmeans, said resilient means yielding to permit said piston to becomesubstantially inoperative when the pressure created by said pump reachesa predetermined degree.

2. A piston pump for conveying liquids comprising a pump casing havingan inlet passage and an outlet passage, a piston reciprocable in saidcasing, driving means adapted positively to. displace said piston in onedirection only, a transmission member located between said driving meansand the piston and extending into said casing to loosely engage one sideof the piston, resilient means for displacing the piston in the otherdirection, a suction valve controlling the inlet passage andcommunicating with that side of the piston remote from the driving meansand a discharge valve communicating with the outlet passage and withthat side of the piston engaged by said transmission member, saidresilient means yielding to permit said piston to become substantiallyinoperative when the pressure created by said pump reaches apredetermined degree.

3. A piston pump for conveying liquids comprising a pump casing havingan inlet passage and an outlet passage, a piston reciprocable in saidcasing, driving means adapted positively to displace said piston in onedirection only, a transmission member located between said driving meansand the piston and extending into said casing to loosely engage one sideof the piston, means for displacing the piston non-positively in theother direction, a suction valve controlling the inlet passage andcommunicating with that side of the piston remote from the driving meansand a discharge valve-communicating with the outlet passage and withthat side of the piston engaged by said transmission member, the meansfor displacing the piston non-positively yielding to permit said pistonto become substantially inoperative when the pressure created by saidpump reaches a predetermined degree.

4. A piston pump for conveying liquids comprising a pump casing havingan inlet passage and an outlet passage, a piston reciprocable in saidcasing, driving means adapted positively to displace said piston in onedirection only, a transmission member located between said driving meansand the piston and extending into said casing to loosely engageone side'of the piston. loading means opposed to said driving means and adaptedto cause displacement of the piston in the other direction, a suctionvalve controlling the inlet passage and communicating with that side ofthe piston remote from the driving means and a discharge valvecommunicating with the outlet passage and with that side of the pistonengaged by said transmission member, said loading means yielding topermit said piston to become substantially inoperative when the pressurecreated by said pump reaches a predetermined d gree.

5. A piston pump for conveying liquids com- Drising'a pump casing havingan inlet e and an outlet passage, a piston reciprocable in said casing,driving means adapted positively'to displace said piston in onedirection only, a transmission member located between said driving meansand the piston and extending into said casing to engage oneside oifithepiston, a resilient buifer interposed between said transmission memberand said driving means, a suction valve controllingthe inlet e andcommunicating with that side of the piston remote from the driving meansand a discharge valve communicating with the outlet passage and withthat side of, the piston engaged by said transmission member.

6. A piston pump 'for conveying liquids comprising a. pump casing havingan inlet passage and an outlet passage, a piston reciprocable in saidcasing, driving means reciprocable through 5 a wall of said pump casingand adapted positively to displace said piston .in one direction only,

resilient means for displacing the'piston in the other direction, asuction valve communicating with the induction side of the piston'and adis-- 7 10 charge valve mounted on the piston and comv and an outletpassage, a piston reciprocable in 1 20 said casing, drivingv meansadapted positively to displace said piston-inonedirection only, atransmission member located betweensaid driving means and the piston andextending into said casing to engage one side of the piston, resilient25 means for displacing the piston in the other direction, a suctionvalve controlling the inlet passage and communicating with that side ,ofthe piston remote from the-driving means and a discharge valve mountedonthe piston and com- 30 municating atall times with the outlet passageand with that-side of the piston engaged by-said transmission member,said resilient means yielding to permit said piston to becomesubstantially inoperative when the pressure created by said 35 pumpreaches a predetermined degree.

8. A pump comprising a pump casing having an inlet and a discharge,valves controlling said inlet and discharge, a piston reciprocable insaid casing, said inlet communicating with one side of 4 saidpiston andsaid discharge communicating with both sides oi said piston, resilientmeans for moving the piston in one direction, and means including a pushrod reciprocable through a wall of said pump casing and looselyconnected to the 45 piston for moving it in the opposite direction, saidresilient means yielding to permit said piston to become substantiallyinoperative when the pressure created by said pump reaches apredetermined degree. I 50 9. A piston pump for conveying liquidscomprising a pump casing having an inlet passage and an outlet passage,a piston reciprocable in said casing, driving means adapted positivelyto displace said piston in one direction only, a trans- 55 missionmember located between said driving means and said piston and extendinginto said casing to loosely engage one side of said piston, resilientmeans urging said transmission mem-v ber into contact with said drivingmeans, resilient means for displacing the piston in the other direction,both of said resilient means tending to move said piston andtransmission member in the same direction, a suction valve controllingthe inlet passage and communicatingwith that side 65 of the pistonremote from the driving means, and a discharge valve communicating withthe outlet passage and with that side of the piston engaged by saidtransmission member.

10. In a pump structure, incombination, a 70 cylinder having an inletadapted to be connected with a source of supply and an outlet adapted tobe connected with a pointof ;u'se, check valves for said inlet andoutlet, a. piston reciprocable in said cylinder and adapted to dischargeliquid 75 therefrom, resilient means constantly urging said piston in adirection to discharge fluid through said outlet, and a plungerreciprocable independently of said piston projecting into said cylinder,said plunger adapted to move said piston against the urge of saidresilient means when in contact 5 with said piston and when moving inopposition, to said resilient means, and being of a size suf ficient todisplace a material amount of fluid from said cylinder through saidoutlet during movement toward and when tree of contact with I saidpiston.

11. In a pump structure,:-in combination, a cylinder having an inletadjacent one end and an outlet adjacent the other end, a piston re-.-ciprocable between said inlet and outlet, spring means constantly urgingsaidpiston'in a direction to discharge fluid through said outlet, acheck valve in said inletpreventing reversal oi flow therethrough, abypass between opposite ends of said piston and communicating with saidoutlet, a check valve in said bypass opening toward said outlet, andmeans at the outlet end of said piston movable relative thereto formoving said piston against the force of said spring means and reducingthe eiiective cross sectional area thereof subject to the pressure offluid at said end, whereby movement of said piston toward the inlet endof said cylinder will displace a greater volume of fluidthrough 'saidbypass to the outlet end of said cylinder than the volmilesimultaneously created at said outlet end by said movement of saidpiston.

12. In a pump structure, in combination, a cylinder having an inletadjacent one end and an outlet adjacent the other end, a pistonreciprocable between .said inlet and outlet, spring means constantlyurging said piston in a direction to discharge fluid through saidoutlet, 9,

check valve in said inlet preventing reversal of flow therethrough, abypassbetween opposite 40 ends of said piston and communicating withsaid outlet, a check valve in said bypass permitting flow therethroughonly in'thej-direction of said outlet, and means at the outlet end ofsaid piston movable relative thereto for moving said piston against theforce of said spring means, said means including a member reducing theeffective cross sectional area of said piston subject to the pressure offluid at said end, whereby movement of said piston toward'the inlet endof said cylinder will displace a greater volume ofjfluid through saidbypass to the outlet end of said cylinder than the volume simultaneouslycreated at said outlet end by said movement of said piston.

13. In a pump structure, in combination, a cylinder having aninletadjacent one end and an outlet adjacent the other end, a pistonreciprocable between. said inlet and outlet, spring means constantlyurging said piston in a direction to dischargefluid through said outlet,a check valve in said inlet preventing reversal of fiow therethrough, abypass in said piston between opposite ends thereof and-communicatingwith said outlet, a check valve in saidbypass permitting flowtherethrough only in the direction of said outlet, driving means movableindependently of said pistonfor moving said piston against the action of'said spring means, and a transmission member between said driving meansand said piston reducing the effective cross-sectional area of the.outlet end of said piston whereby movement of said piston toward theinlet end ofsaid cylinder will displace a greater volume'of fluidthrough said bypass to the outlet endoi' said'cylinder than the volumesimultaneouslycreated at said outlet end by said movement of saidpiston.

14. In a pump structure, in combination, a cylinder having an inletadjacent one end and an outlet adjacent the other end, a pistonreciprocable between said inlet and outlet, means urging said pistontoward the outlet end of said cylinder, a check valve in saidinletpreventing reversal of flow therethrough, a bypass between opposite endsof said piston and communicating with said outlet, a check valve in saidbypass opening toward said outlet, and a member at the outlet end ofsaid piston 'engageable therewith to move it against the force of saidmeans and reducing the efiective cross-sectional area of said pistonsubject to the pressure of fluid at said end, whereby movement of saidpiston toward the inlet end of said' cylinder will displace'a greatervolume of fluid through said bypass to the outlet end of said cylinderthan the volume simultaneously created atsaid outlet end by saidmovement of said piston, said member being movable independently of saidpiston whereby when it is moving relative to and toward said piston itacts to displace fluid from said outlet end of said cylinder.

15. In a pump structure, in combination, a housing providing a cylinderhaving an inlet adjacent one end and an outlet adjacent the other end, apiston reciprocable between said inlet and outlet, spring meansconstantly urging said piston in a direction to discharge fluid throughsaid outlet, a check'valve in said inlet preventing reversal of flowtherethrough, a bypass in said housing between opposite ends of saidpiston and communicating .with said outlet, a check valve in said bypassopening toward said outlet, a member reciprocable independently of saidpiston engageable therewith for moving it in one direction against theaction of said spring means, said member reducing the effective crosssectional area of the outlet end of said piston whereby movement of saidpiston toward the inlet end of said cylinder will displace a greatervolume of fluid through said bypass to the outlet end of said cylinderthan the volume simultaneously created at said outlet end by saidmovement of said piston, and means for positively moving said memberinat least one direction. 1

16. In a pump structure, in combination, a cylinder having an inlet andan outlet, a check valve for said inlet, a piston reciprocable in saidcylinder and adapted to discharge liquid therefrom, resilient meansconstantly urging said piston in a direction to discharge fluid fromsaid cylinder through said outlet, a plunger of a diameter diflerentfrom said piston projecting into said cylinder and adapted to abut andmove said piston against the action of said resilient means, saidplunger being reciprocable independently of said piston and adapted todisplace a material amount of liquid from said cylinder through saidoutlet when moving toward abutting relation with respect to said piston,and means including a check valve opening toward said outlet forbypassing fluid in said cylinder from the inlet thereof to the outletthereof.

MAX HURST.

